Dust Control Handbook for Industrial Minerals Mining and Processing

The OASIS is a relatively simple design and system. Mill air is drawn into the unit and passesthrough a primary filtering chamber, normally using HEPA quality filters. After the air exits theprimary chamber, it passes through an optional heating or cooling area, which can beincorporated into the unit if temperature control is desired. The air then flows through adistribution manifold filter when exiting the unit. This provides an even distribution of cleanfiltered airflow down over the worker, while providing backup filtering in case there is a problemwith the primary filtering chamber. If the bagging or palletizing process generates a significantamount of dust, it will contaminate the envelope of clean air from the OASIS after it flows downover the worker. In these cases, it is normally advisable to then capture this dust-laden air withan LEV system.Figure 6.12. OASIS positioned over bag operator to deliver clean filtered air down over work area.With the OASIS, the target is to have an average velocity of roughly 375 fpm flowing down overthe worker, which normally keeps any dust-laden mill air from entering the clean air core[Volkwein et al. 1986]. One important feature with an OASIS system is to incorporate a selfcleaningprimary filter design. There are a number of different self-cleaning techniques used toremove the dust cake from the filters. For example, the reverse air jet pulse collector is a verycommon and effective method to perform this task (refer to Chapter 1—Fundamentals of DustCollection Systems).The OASIS is very effective at lowering workers' respirable dust exposures. A bag operator'srespirable dust exposure was reduced by 82 and 98 percent at two different operations using theOASIS, as compared to when the unit was not being operated [Robertson 1986]. At both ofBagging 171